Mention 64 Source limit;

api/init.lua

@@ -1969,10 +1969,17 @@ return {
               description = "Plays the Source.  This doesn't do anything if the Source is already playing.",
               key = "Source:play",
               module = "lovr.audio",
+              notes = "There is a maximum of 64 Sources that can be playing at once.  If 64 Sources are already playing, this function will return `false`.",
               variants = {
                 {
                   arguments = {},
-                  returns = {}
+                  returns = {
+                    {
+                      name = "success",
+                      type = "boolean",
+                      description = "Whether the Source successfully started playing."
+                    }
+                  }
                 }
               }
             },

api/lovr/audio/Source/play.lua

@@ -2,5 +2,15 @@ return {
   summary = 'Play the Source.',
   description = 'Plays the Source.  This doesn\'t do anything if the Source is already playing.',
   arguments = {},
-  returns = {}
+  returns = {
+    {
+      name = 'success',
+      type = 'boolean',
+      description = 'Whether the Source successfully started playing.'
+    }
+  },
+  notes = [[
+    There is a maximum of 64 Sources that can be playing at once.  If 64 Sources are already
+    playing, this function will return `false`.
+  ]]
 }